Previously, you had your "Inbox," and an "Other" folder where messages from people who aren't friends or friends-of-friends would end up. But it replaced this second folder with "Message Requests" — which let people you're not connected with ask to be able to talk.

But what very few people realise is there is now also a third category of messages: Filtered Message Requests. These filtered messages are what Facebook thinks is spam, and so doesn't even notify you about. They're also not easy to find.

There are many more cases like this. Some are recent, while other messages appear to have been sent before the Filtered Message Requests inbox was introduced, and were then automatically moved to it once it was launched — all without ever being read.

Went through my Facebook filtered messages and realised there was a message from a long lost friend from like half a year ago 😭😭😭 I SORRY

The situation is made doubly frustrating by the fact that one of the big reasons for the change to Message Requests (and Filtered Message Requests) is to prevent things like this happening.

Tony Leach, a product manager at Facebook, told TechCrunch back when Message Requests launched: "We’ve heard so many stories like estranged parents trying to get back in touch, or you lost your wallet and someone trying to get in touch with you ... That’s why we want to replace that with a system that makes it a lot easier to catch the messages that you want to see."

Clearly, this hasn't been a complete success.

But what can Facebook do about this? It's a tricky one. If it errs on the side of caution, and filters more, then important messages will continue to fall through the cracks. But if it relaxes its filters, then more spam will likely get through too — and people will complain. (Facebook did not immediately respond to a request for comment.)

Daniel Emery, who missed the message telling him of his friend's death, would like Facebook to modify its messaging feature to add a more straightforward spam folder.

"Gmail and Google, for all its flaws, has a pretty sensible system," he told Business Insider. "There is a folder for spam, you can look into it if you want, you can pull things out. It's not hidden from you, and I think the issue with this is it's kind of a bit too much 'nanny state.'"

He added: "Facebook is trying to be overprotective. Overprotective comes at a cost, and things like this happening are exactly that ... hiding it is never a good thing."

If you want to check your Filtered Message Requests in the mobile app, load up Settings, then click on "People," then click on "Message Requests," then click on "See filtered requests." If you're on the desktop version of Facebook, click on the drop-down Messages tab, then on "Message Requests," then press "See filtered requests." For more detailed instructions, read this »